1. Technical Field
The invention relates to a document reading apparatus for reading characters or images on a document.
2. Related Art
Stationary scanners are widely used as a document reading apparatus (also called an image reading apparatus). In the stationary scanners, the scanning of a document is accomplished by moving either of a document reading portion or a document arranged in the interior of the apparatus. On the other hand, handy scanners are also known which read a document by moving (scanning) the document reading apparatus body. The handy scanner includes a position detection sensor for sensing the movement direction and the movement amount of the scanner. At least two position detection sensors are required for detecting curved movements of the scanner.
Examples of the above described related art are disclosed in JP-A-8-139868 and JP-A-9-282084.
However, since the handy scanner is constituted so that the body of the scanner is moved, the body of the scanner may go beyond a document when scanning an end of the document, for example, the upper end thereof. When the body of the scanner goes beyond the document, it is not possible to detect the movement direction and the movement amount of the scanner, if one of the two position detection sensors goes beyond from the document. Therefore, in all reading conditions, at least four position detection sensors are required for achieving a high degree of accuracy in reading.
Two position detection sensors are required for detecting the movement direction and the movement amount of the scanner. For this reason, when four position detection sensors are provided, there exists a problem of the increase in cost. In addition, there exists another problem that a space for arranging four position detection sensors is also required, and further reduction of the size of the handy scanner, or of the complexity of the design is restricted.